Reporting an error early in the python startup, before importing is properly initialized, can be tricky.
For example, here:

if (PyImport_ImportFrozenModule("_frozen_importlib") <= 0) {
  Py_FatalError("Py_Initialize: can't import _frozen_importlib");

The problem is, that _Py_DisplaySourceLine will set an exception because it cannot import the io module.  And this will terminate the traceback output.

The attached patch aims to rectify it by ignoring errors from this api in traceback.c